SPINAL NERVES IN VERTEBRATES 151 



branches from above and one from the rear, one of which joins 

 the peripheral plexus above. A conspicuous lateral branch 

 (fig. 1, R.Cut.S.) is received by each dorsal sensory ramus at the 

 dorsal border of the myotomes, coming from the inner surface 

 of the skin. This is doubtless the ramus cutaneus superior of 

 Co^.e's figure 1. In like manner a lateral-dorsal branch is given 

 off to the skin from each ventral sensory ramus, a little below 

 the ventral border of the myotomes. It is apparently Cole's 

 Ramus cutaneus medius (fig. 1, R.Cut.M.). In this particular 

 region, where the main sensory rami continue upward and down- 

 ward to supply the dorsal and anal fins and the above cutaneous 

 rami appear to be branches of the main trunks, a change 

 of nomenclature might prove advantageous. For the dorsal 

 branch I would suggest Ramus cutaneus lateralis superior and 

 for the ventral branch R. cutaneus lateralis inferior. 



The long distance that the motor and sensory roots (fig. 1) 

 travel within the membranous neural canal certainly supports 

 the supposition that the skeletal axis continues to grow after 

 the neural axis has obtained its growth or to be more specific 

 grows more rapidly than the neural axis. It ^\ill be seen from 

 figure 1 that the motor or ventral roots extend for longer dis- 

 tances than the dorsal or sensory within the neural canal, which 

 in some instances is nearly a segment. As in the cephalic region 

 the sensory fibers enter the latero-dorsal surface of the spinal 

 cord as a single bundle or root, and the point of entrance is about 

 on a level with the posterior border of the previous spinal gan- 

 glion. Occasionally it may be slightly cephalad or caudad of 

 this point. Like the more cephalic nerves, the caudal nerves 

 usually have a cephalic and a caudal motor or ventral root 

 {V.R. {1) and V.R. (2) ), which ordinarily take origin from sev- 

 eral rootlets, generally more for the cephalic root. The last 

 three motor rami show an irregularity in having but one motor 

 root each. Of these three roots the first one has two rootlets and 

 the last two, one rootlet each. Usually both motor roots of a nerve 

 have separate foramma, situated a little behind their respective 

 ganglia, about on a level with the upper surface of the noto- 

 chord. In one or two of the first nerves in figure 1 the caudal 



